Linear Dimensions of Adsorbed Semiflexible Polymers: What can be learned about their persistence length?

Conformations of partially or fully adsorbed semiflexible polymer chains are studied varying both contour length $L$, chain stiffness, $kappa$, and the strength of the adsorption potential over a wide range. Molecular Dynamics simulations show that partially adsorbed chains (with tails, surface attached trains and loops) are not described by the Kratky-Porod wormlike chain model. The crossover of the persistence length from its three-dimensional value $(ell_p)$ to the enhanced value in two dimensions $(2ell_p)$ is analyzed, and excluded volume effects are identified for $L gg ell_p$. Consequences for the interpretation of experiments are suggested. We verify the prediction that the adsorption threshold scales as $ell_p^{-1/3}$.